This invention relates generally to plug containers and more particularly, but not by way of limitation, to a compact plug container having a split-ring retained, splined coupling for connecting with a casing collar adaptor.
One operation which is often conducted during the completion of an oil or gas well is a cementing operation wherein fluid cement is pumped down the central bore of a well casing and out around the bottom of or the side of the well casing into an annulus between the well casing and the oil well borehole where the cement is allowed to harden to provide a seal between the well casing and the well borehole.
At the beginning of a typical cementing job, in rotary drilled wells, the well casing and the well borehole are usually filled with drilling mud. To reduce contamination at the interface between the drilling mud and the cement which is pumped into the well casing on top of the drilling mud, a bottom cementing plug is pumped ahead of the cement slurry so that the interface between the cement slurry and the drilling mud already in the well casing is defined by the bottom cementing plug.
As the cement is pumped into the well casing, the bottom cementing plug is pumped down the well casing. As it travels, the plug wipes mud from the walls of the casing ahead of the cement slurry, thereby reducing dilution of the cement slurry. When this bottom cementing plug reaches a predetermined plug stop, generally a float collar or float shoe located in a portion of the well casing, the bottom cementing plug seats and the differential pressure due to the high pressure cement located above the bottom cementing plug ruptures a diaphragm of the bottom cementing plug to allow the cement slurry to proceed down through the plug and then through the appropriate ports into the annulus between the well casing and the borehole.
At the completion of the mixing of the cement slurry, a top cementing plug is pumped into the well casing to similarly define an interface between the upper level of the cement slurry within the well casing and displacement fluid which is pumped in on top of the cement slurry. This top cementing plug is solid and when it is pumped to a pressure shut-off, the displacement of cement is terminated.
It is desirable to be able to place the cementing plugs in the well casing without opening the well casing. In such a situation, a plug container is mounted on top of the well casing. This plug container holds one or more of the cementing plugs and includes a mechanical retaining means which keeps the plugs from entering the well casing until the desired time.
Prior types of such plug containers have central bodies for holding one or more plugs, which bodies can have a plurality of ports for receiving the cement flows either above or below the positions where the plugs are held. These prior types of plug containers generally have casing adapters which are either threaded or integrally formed with the main bodies of the plug containers. The free ends of these adapters are threaded or clamped to the casing for connecting the plug container to the casing. Some prior types of plug containers have plug-receiving chambers with internal diameters which are greater than the outer diameters of the plugs retained within the chambers. Some prior art plug containers have internally threaded end plugs with pressure-energized seals and solid plug abutments. These end plugs, or caps, permit ready access to the internal chamber of the plug container such as for placing a plug therein or for connecting another plug container thereto.
Although there are prior art types of plug containers which include one or more of the aforementioned features, I am not aware of any plug container which combines each of these features in a single compact, versatile plug container. Furthermore, I am not aware of any such plug container which also enables the casing adapter to be quickly connected in a splined, clamped relationship to the main body of the plug container. Because plug containers can be bulky and hard to handle, there is the need for such a compact, versatile plug container which can be readily used at a well site.